Different shouldn't mean worse
Will attempt to respond to your points one by one.
I don't have a synopsis of all Canadian medical research at my fingertips. But, an anecdote comes to mind. Paul Tsongas of Massachusetts, after receiving considerable campaign financing from the U.S. health insurance industry, boldly asserted that if he'd gotten sick in Canada, he would have died. I then read that the treatment that saved his life was developed in Canada. I haven't researched this further in recent times. But, it wouldn't be the first time that the U.S. health insurance disinformation system had worked its magic on one or another U.S. citizen.
I don't know if the life expectancy of the U.S. would improve solely by implementing national health care. But, it's easier to compare a single number with a single number than it is to compare one set of a million health care outcomes with another million outcomes. Citing this figure comes in response to the U.S. contention that its system is superior to Canada's (at least some people contend that). Citing a a higher Canadian life expectancy is one way to refute this. If more medically specific data is available to support the U.S. system, by all means present it.
I'm sure there are other factors in the life expectancy result. But, will it feel any better to admit that some other factor of American life is the cause? People commonly cite violent crime. But, I've read that while tragic, this is not a statistically significant contribution. I suspect unhealthy living in the form of diet, alcohol, and exercise are probably the other major culprits.
Where would the Canadians go? I've heard of Canadians, with cash in hand, crossing the border south to pay expenses out of pocket to get care in the U.S, and avoid waiting lines in Canada. But, I wonder how prevalent this is. I have literally hundreds of relatives and friends in Canada and have never heard of one crossing into the U.S. to get health care. But, you make a point. A system public or private, has just so many resources to address so many tasks. If one is short of resources, the system will give somewhere. In Canada it results in waiting lines. In the U.S., the price goes up. If you're rich and don't want to wait, the U.S. is the better place to be. If not, Canada is.
Few private sector employees get health benefits that even come close to the state and federal benefits. Some big corporations may have done this in the past. But, you want ER (which this forum is dedicated to), good luck getting free health care for life from your former employer. I've never met anyone with such a benefit. And, the states are going broke paying for such benefits for public "servants" and politicians. There is a massive imbalance there.
The 20 mill or more illegal immigrants do indeed distinguish the U.S. from other countries. But, the U.S., at least a significant part of it, seems to want the cheap labor. I think this helps make my point. These illegals are eligible for free govt health care at least at emergency rooms, while the citizens paying for their are aren't. Are you saying that illegal immigration actually justifies denying free care to taxpaying citizens that when such care is provided to the illegals (who frequently pay little or no tax)??
In Canada it would be the other way around. The citizen would get free (by "free" I mean without a cost in addition to the standard tax level) health care, and the "visitor", legal or not, would have to pay. I know because I once visited Canada while a U.S. resident (though still a Canadian citizen) and had an appendectomy while in Toronto. Since I wasn't covered under the Canadian system at the time, the Canadian hospital demanded, and received, compensation from my Boston area HMO.
This goes to my point that the U.S. already has national health care: the old, the poor, and any penniless person at an emergency room. It's ironic that it's even more "resdistributive" than the Canadian system. Again, in Canada, although middle class people do pay taxes into the health care system, it actually gets them something. It seems to me that American taxpayers, by comparison, are being shafted.